WO2020262706A1

WO2020262706A1 - Fixing belt unit and fixing device

Info

Publication number: WO2020262706A1
Application number: PCT/JP2020/025930
Authority: WO
Inventors: 武木下; 石川　潤司
Original assignee: キヤノン株式会社
Priority date: 2019-06-28
Filing date: 2020-06-25
Publication date: 2020-12-30
Also published as: US20220091547A1; US11693344B2

Abstract

A heater 600 comprises a substrate 610 and a plurality of heating elements 623a-623f that are provided on both surfaces of the substrate 610 and generate heat by the passage of electric current, and heats a fixing belt by being brought into contact with the inner peripheral surface of the fixing belt. The plurality of heating elements 623a-623f have lengths different from each other in the width direction, and at least three heating elements are provided on the front surface of the substrate 610 on the side on which the heater 600 comes into contact with the inner peripheral surface of the fixing belt, and at least one heat element is provided on the back surface thereof. The heating element 623b having the longest length in the width direction among the plurality of the heating elements 623a-623f is provided on the front surface. Regarding the heating elements 623a-623c provided on the front surface, the heating element 623b having the longest length in the width direction is disposed between the heating element 623a and the heating element 623c with respect to the rotation direction of the fixing belt.

Description

Fixing belt unit and fixing device

The present invention relates to a fixing belt unit used for a fixing device for fixing a toner image on a recording material, and a fixing device including the fixing belt unit.

As a fixing device, a configuration in which a fixing belt for heating a recording material is heated by a heater has been conventionally known. Further, as a heater, a configuration has been proposed in which heating elements having different lengths are arranged on both sides of a substrate so that heating can be performed according to the size of a recording material (Japanese Patent Laid-Open No. 2016-24321).
[Problems to be solved by the invention]

In a configuration in which three or more heating elements having different lengths are provided on one side of the substrate and the selected heating elements are energized, the heating element having the longest length on one side of the substrate in the transport direction of the recording material. If is provided, there are the following problems. The heating element with the longest length has the largest calorific value. As a result, when only the longest heating element is energized, the temperature difference between one end side and the other end side of the substrate becomes large in the transport direction, which may cause distortion of the substrate. Therefore, a configuration that reduces the distortion of the substrate caused by energizing the longest heating element is desired.
[Effect of the invention]

According to the present invention, it is possible to reduce the distortion of the substrate caused by energizing the longest heating element.

FIG. 1 is a schematic configuration sectional view of the image forming apparatus according to the first embodiment.

FIG. 2 is a schematic configuration sectional view of the fixing device according to the first embodiment.

FIG. 3 is a configuration diagram of a heater and a heater control circuit according to the first embodiment.

In FIG. 4, (a) is a schematic configuration plan view of the back surface side of the heater according to the first embodiment, (b) is a schematic configuration plan view of the same front surface side, and (c) is an AA cross section of (a). It is a figure.

FIG. 5 is a graph showing the relationship between the position of the heating element in the transport direction of the recording material of the fixing nip portion and the power input to the heating element for setting the temperature of the fixing film to a predetermined temperature.

In FIG. 6, (a) is a schematic configuration plan view of the back surface side of the heater according to the second embodiment, and (b) is a schematic configuration plan view of the front surface side as well.

The first embodiment will be described with reference to FIGS. 1 to 5. First, the schematic configuration of the image forming apparatus of this embodiment will be described with reference to FIG.
[Image forming device]

The image forming apparatus 100 shown in FIG. 1 is an electrophotographic full-color printer having four color (yellow, magenta, cyan, black) image forming portions PY, PM, PC, and PK in the apparatus main body. In the present embodiment, the image forming unit PY, PM, PC, and PK are arranged along the rotation direction of the intermediate transfer belt 8 described later in an intermediate transfer tandem system. The image forming apparatus 100 produces a toner image (image) in response to an image signal from a document reading device (not shown) connected to the apparatus main body or a host device such as a personal computer communicatively connected to the apparatus main body. It is formed on the recording material S. Examples of the recording material include sheet materials such as paper, plastic film, and cloth.

First, the transfer process of the recording material of the image forming apparatus 100 will be described. The recording material S is stored in a form of being loaded in the cassette 62, and is fed one by one to the transport path 64 by the feed roller 63 according to the image formation timing. Further, the recording materials S loaded on the bypass tray (not shown) may be fed to the transport bus 64 one by one. When the recording material S is conveyed to the registration roller 65 arranged in the middle of the transfer path 64, the registration roller 65 performs skew correction and timing correction of the recording material S, and then moves to the secondary transfer unit T2. Sent. As will be described later, the secondary transfer portion T2 is a transfer nip portion formed by a portion of the intermediate transfer belt 8 stretched on the secondary transfer inner roller 66 and the secondary transfer outer roller 67. In the secondary transfer unit T2, the toner image is secondarily transferred from the intermediate transfer belt 8 to the recording material S by applying the secondary transfer voltage to the secondary transfer inner roller 66.

The process of forming the toner image sent to the secondary transfer unit T2 at the same timing as the transfer process of the recording material S to the secondary transfer unit T2 described above will be described. First, the image forming units PY to PK will be described. However, the image forming units PY to PK are configured to be substantially the same except that the toner colors used in the developing

devices

4Y, 4M, 4C, and 4K are different from those of yellow, magenta, cyan, and black. Therefore, in the following, the yellow image forming unit PY will be described as an example, and the other image forming units PM, PC, and PK will be omitted.

The image forming unit PY is mainly composed of a photosensitive drum 1Y, a charging device 2Y, an exposure device 3Y, a developing device 4Y, and the like. The surface of the photosensitive drum (cylindrical photosensitive member) 1Y as a rotationally driven image carrier is uniformly charged in advance by the charging device 2Y, and then driven based on the signal of image information. An electrostatic latent image is formed by 3Y. Next, the electrostatic latent image formed on the photosensitive drum 1Y is developed by the developing device 4Y with toner and visualized as a toner image. After that, a predetermined pressing force and a primary transfer bias are applied by the primary transfer rollers 5Y arranged to face each other across the photosensitive drum 1Y and the intermediate transfer belt 8, and the toner image formed on the photosensitive drum 1Y is displayed on the intermediate transfer belt 8. Primary transfer to. A small amount of transfer residual toner remaining on the photosensitive drum 1Y after the primary transfer is removed by a cleaning blade or the like (not shown), and the toner is prepared for the next image forming process again.

The intermediate transfer belt 8 as an intermediate transfer body is stretched by a tension roller 10, a secondary transfer inner roller 66, and a drive roller 7. Then, the intermediate transfer belt 8 is driven by the drive roller 7 so as to move in the direction of arrow R2 in the drawing. The image forming process of each color processed by the above-mentioned image forming units PY to PK is performed at the timing of sequentially superimposing on the toner image of the color upstream in the moving direction that is primarily transferred on the intermediate transfer belt 8. As a result, a full-color toner image is finally formed on the intermediate transfer belt 8 and conveyed to the secondary transfer unit T2. The transfer residual toner after passing through the secondary transfer unit T2 is removed from the intermediate transfer belt 8 by the transfer cleaner device 11.

The toner image is secondarily transferred from the intermediate transfer belt 8 to the recording material S by the transfer process and the image formation process described above. After that, the recording material S is conveyed to the fixing device 30, and the toner image is melt-fixed on the recording material S by being pressurized and heated by the fixing device 30. The recording material S on which the toner image is fixed is discharged onto the discharge tray 601 by the discharge roller 69. The image forming apparatus 100 includes a control unit 300 for performing various controls such as the above-mentioned image forming operation. Further, the above-mentioned series of image forming operations is controlled by the operation unit 110 on the upper surface of the apparatus main body or the control unit 300 according to each input signal via the network.
[Fixing device]

Next, the fixing device 30 of the present embodiment will be described with reference to FIG. Here, the fixing device is required to shorten the warm-up time due to a rapid temperature rise and to support recording materials of various sizes. When reducing the heat capacity of the heater of the fixing device in order to shorten the warm-up time, it is conceivable to provide a heater provided with only a heating element having a length that matches the width of the maximum size recording material. However, in this case, the temperature of the non-passing region where the recording material does not pass through the fixing nip portion becomes too high with respect to the passing region where the recording material passes through the fixing nip portion. For this reason, it has been conventionally required to suppress the temperature rise in the non-passing region. In the present embodiment, the heater 600 of the fixing device 30 is configured to have a plurality of heating elements corresponding to the sizes of the plurality of recording materials, so that the temperature rise in the non-passing region is suppressed.

As shown in FIG. 2, the fixing device 30 of the present embodiment includes a fixing belt unit 60 and a pressure roller 70, and is detachably provided on the main body of the image forming device 100 (see FIG. 1). .. The fixing belt unit 60 has a fixing belt 650 and a heater 600, which will be described in detail later, and the fixing belt 650 is heated by the heater 600.

The nip forming member and the pressure roller 70 as a rotating body are rotatably supported by the apparatus main body. Further, the pressure roller 70 is arranged so that its longitudinal direction is parallel to the fixing belt unit 60, abuts on the outer peripheral surface of the fixing belt 650 of the fixing belt unit 60, and is pressed against the fixing belt unit 60. It is provided so as to. The pressure roller 70 includes, for example, an elastic layer 72 such as silicone rubber having a thickness of about 3 mm on the outer periphery of a metal (for example, stainless steel) core metal 71, and PTFE, PFA, having a thickness of about 40 μm on the outer periphery of the elastic layer 72. It has a release layer 73 made of a fluororesin such as FEP. The pressure roller 70 is rotatably supported by the device frame by rotatably holding both ends of the core metal 71 between the side plates of the device frame (not shown) of the fixing device 30.

A fixing nip portion N is formed between the fixing belt 650 and the pressure roller 70 as described later. Therefore, when the pressurizing roller 70 is rotated by a motor (not shown), the rotational force of the pressurizing roller 70 is transmitted to the fixing belt 650 by the frictional force generated in the fixing nip portion N. In this way, the fixing belt 650 is rotationally driven by the pressure roller 70 (so-called pressure roller drive system). The recording material S is sandwiched and conveyed by the fixing nip portion N formed by the rotating pressure roller 70 and the fixing belt 650.

In the fixing device 30, when the pressure roller 70 is rotationally driven and the cylindrical fixing belt 650 is brought into a driven rotation state, the heater 600 is energized. Then, when the temperature of the heater 600 rises to the target temperature and the temperature is adjusted, the recording material S carrying the unfixed toner image on the fixing nip portion N is guided and introduced along an entrance guide (not shown).

In the fixing nip portion N, the toner image supporting surface side of the recording material S is in close contact with the outer surface of the fixing belt 650, and the recording material S moves together with the fixing belt 650. In the process of sandwiching and transporting the recording material S at the fixing nip portion N, heat from the heater 600 is applied to the recording material S via the fixing belt 650, and the unfixed toner image is melt-fixed on the recording material S. The recording material S that has passed through the fixing nip portion N is separated from the fixing belt 650 and discharged.
[Fixing belt unit]

Next, the configuration of the fixing belt unit 60 will be described in detail. The fixing belt unit 60 is provided on the main body of the apparatus so as to be movable toward the pressure roller 70 side. The fixing belt unit 60 has a fixing belt 650, a heater holder 660, a stay 670, and a heater 600 arranged in a non-rotating manner inside the fixing belt 650.
[Fixing belt]

The fixing belt (fixing film) 650 is formed in an endless shape (cylindrical shape) and has flexibility, and in the case of the present embodiment, it is a thin film-like belt. In such a fixing belt 650, an elastic layer is formed on a base material, and an outermost surface layer is further formed on the elastic layer. The base material is, for example, stainless steel formed into a cylindrical shape having a thickness of 30 μm. The elastic layer is, for example, a silicone rubber layer (elastic layer) having a thickness of about 300 μm, and is formed on the base material by an appropriate method such as a ring coating method. The outermost surface layer is, for example, a PFA resin tube having a thickness of 20 μm, and covers the elastic layer. Then, grease as a lubricant is applied to the inner peripheral surface of the fixing belt 650. This is to improve the slidability between the inner peripheral surface of the fixing belt 650 and the heater holder 660. As the base material of the fixing belt 650, a nickel-based metal material, a heat-resistant resin such as polyimide, or the like may be used in addition to stainless steel.

The fixing belt 650 is removable from the heater holder 660, which will be described later, and is rotatable and wide by flanges (not shown) arranged at both ends in the width direction (longitudinal direction) intersecting the rotation direction of the fixing belt 650. It is supported to regulate directional movement. That is, the flange portion is fitted inside the width direction end portion of the fixing belt 650, and the cylindrical portion that rotatably supports the width direction end portion and the abutting portion that can come into contact with the width direction end edge of the fixing belt 650. And have. The cylindrical portion guides the rotation of the fixing belt 650 while holding the end portion in the width direction of the fixing belt 650 in a cylindrical state from the inside.

Here, the pressure roller 70 and the fixing belt 650 may be arranged in a state of being slightly deviated from parallel due to an attachment error of the pressure roller 70 or the fixing belt unit 60 or the like. In that case, the fixing belt 650 can move closer to the width direction while rotating in the arrow X direction in the drawing by the rotating pressure roller 70. Therefore, when the fixing belt 650 moves closer to the width direction, the contact portion of the flange portion receives the end portion in the width direction of the fixing belt 650 and restricts the movement of the fixing belt 650 in the width direction. By attaching the heater holder 660 and the stay 670 to the flange portion, the heater holder 660 and the stay 670 are arranged non-rotatingly inside the fixing belt 650. The flange portion is held by a side plate (not shown) of the fixing belt unit 60 or the like.
[stay]

The stay 670 is, for example, a metal rigid member (sheet metal) extending in the width direction along the fixing belt 650, and here, the cross section is formed in a substantially U shape so as to have an opening on the heater holder 660 side. The stay 670 reinforces the heater holder 660 so that the heater holder 660 is not deformed by the pressing force acting between the fixing belt unit 60 and the pressurizing roller 70. The stay 670 has the above-mentioned flange portions fixed to both ends in the width direction. The flange portions at both ends are pressed toward the pressurizing roller 70 with a predetermined pressing force (for example, 90 to 320 N) by a pressurizing mechanism (not shown). As a result, the pressing force acts on the fixing belt 650 from the flange portion via the stay 670 and the heater holder 660, and the fixing belt 650 and the pressure roller 70 are pressed against each other with a desired pressure contact force. By pressing the fixing belt 650 and the pressure roller 70 into pressure contact, a fixing nip portion N having a predetermined width in the transport direction of the recording material S is formed between the fixing belt 650 and the pressure roller 70. The recording material S on which the toner image is formed is pressurized and conveyed by the fixing nip portion N. The stay 670 may be formed in a shape that rubs against the inner peripheral surface of the fixing belt 650.
[Heater holder]

The heater holder 660 is formed of a resin member having high heat resistance and high heat insulation, such as a liquid crystal polymer resin, and plays a role of holding the heater 600 described later and guiding the fixing belt 650. The heater holder 660 is formed in a shape in which a fitting groove capable of fitting and holding the heater 600 extends along the width direction on the surface opposite to the surface on the stay 670 side (fixing nip portion N side). .. The surface of the heater 600 held by the heater holder 660 is in contact with the inner peripheral surface of the fixing belt 650, and can heat the rotating fixing belt 650. As a result, when the recording material S is sandwiched and conveyed by the fixing nip portion N, the heat generated by the heater 600 is conducted to the recording material S via the fixing belt 650, and the unfixed toner image is heated and melted. It is fixed on the recording material S. The heater 600 is controlled by a heater control circuit 200 described later. Details of the heater 600 and the heater control circuit 200 will be described later (see FIG. 3 below).
[heater]

The heater 600 as a heating member has an insulating, heat-resistant, low-heat capacity substrate 610 having a width direction (which is also a direction orthogonal to the direction in which the recording material is conveyed by the fixing nip portion N), and a plurality of heating elements 623a. It has ~ 623f and protective glass 611 (FIGS. 4A to 4C). In this embodiment, three heating elements 623a to 623f are provided on the front and back surfaces of the substrate 610 so as to have a plurality of heating elements of three or more on at least one surface. The protective glass 611 is provided on the front and back surfaces of the substrate 610 to ensure insulation. Then, as described above, the heater 600 is fixedly supported by the heater holder 660. Such a heater 600 is a ceramic heater having a low heat capacity capable of raising the temperature with a steep rising characteristic by supplying electric power to any one of the heating elements 623a to 623f.

A polyimide layer having a thickness of, for example, about 10 μm is formed as a rubbing layer on the surface side of the heater 600 that comes into contact with the inner peripheral surface of the fixing belt 650. By forming the polyimide layer on the heater 600, the rubbing resistance between the fixing belt 650 and the heater 600 can be reduced, thereby reducing the driving torque for rotating the fixing belt 650 and reducing the wear caused by the rubbing of the fixing belt 650. Can be planned. When a heat-resistant resin such as polyimide is used as the base material of the fixing belt 650, the polyimide layer as the sliding layer of the heater 600 may be omitted. The detailed configuration of the heater 600 will be described later.
[Temperature sensor]

In this embodiment, in order to control the temperature of the fixing belt 650, a temperature sensor 630 that detects the temperature of the heater 600 is provided. In this embodiment, for example, a contact type temperature sensor 630 such as a thermistor sensor is adopted. However, the temperature sensor 630 may be a non-contact type. The temperature sensor 630 is arranged in the heater holder 660 so that the detection unit contacts the back surface of the heater 600 opposite to the fixing belt 650. Further, one temperature sensor 630 is arranged at the center of the heater 600 in the width direction and the longitudinal direction, and detects the temperature near the center of the heater 600. Then, the common temperature sensor 630 controls the temperature adjustment of the plurality of heating elements provided in the heater 600. The number of temperature sensors 630 is not limited to one, and a plurality of temperature sensors 630 may be arranged along the width direction of the fixing belt 650. Further, when there are a plurality of temperature sensors 630, they may be arranged so as to be offset in the rotation direction of the fixing belt 650.
[thermostat]

Further, in the present embodiment, the thermostat 631 is provided so that the power supply to the heater 600 can be cut off when the temperature of the heater 600 exceeds a predetermined temperature. The thermostat 631 is arranged on the heater holder 660 on the back surface side of the heater 600. In the thermostat 631, for example, when the temperature rises above a predetermined temperature, the bimetal reverses and opens the contacts to cut off the power supply, and when the temperature becomes lower than the predetermined temperature, the bimetal returns before reversal and closes the contacts to start power supply. It is a switch to do.
[Heater control]

Next, the control of the heater 600 will be described with reference to FIG. In this embodiment, the heater unit 680 is composed of the heater 600, the temperature sensor 630, and the thermostat 631. The heater unit 680 is controlled by the heater control circuit 200. The heater control circuit (driver circuit) 200 is for adjusting a heat generation state including turning on / off of energization of the heater 600 under the control of the control unit 300. The heater 600 is provided so as to be freely connectable to the heater control circuit 200.

The control unit 300 controls the entire image forming apparatus 100 in addition to controlling the heater 600. Such a control unit 300 includes a CPU (Central Processing Unit) 301, a ROM (Read Only Memory), and a RAM (Random Access Memory). ) Etc. The CPU 301 controls each part while reading a program corresponding to the control procedure stored in the ROM. In addition, work data and input data are stored in the RAM, and the CPU 301 controls by referring to the data stored in the RAM based on the above-mentioned program or the like. The control unit 300 may be prepared exclusively for controlling the heater 600 such as a microcomputer. In this case, it may be provided in the fixing device 30.

In the case of the present embodiment, the control unit 300 acquires the detection result of the temperature sensor 630, and the heater 600 is maintained at the target temperature (for example, around 200 ° C.) based on the acquired detection result. The heat generation state of the heater 600 changes according to the control of the power supply (energization) to the heater 600 by the heater control circuit 200 that can control the control circuit 200.

As for the electric power for generating heat of the heater 600, the electric power generated by the commercial power source 400 is supplied through the heater control circuit 200. The DC power supply 410 is a switching power supply (ADCC power supply) that supplies electric power to each load on the secondary side in the image forming apparatus. The DC power supply 410 generates secondary DC voltages "5V" and "24V" from the AC voltage "100V" output by the commercial power supply 400. The DC voltage "5V" generated by the DC power supply 410 is used to drive the control unit 300 and the like, and the DC voltage "24V" is used to drive the triac drive circuits 231a to 231f described later. The temperature sensor 630 has a characteristic that the resistance value decreases as the temperature rises, and the temperature can be detected by the partial pressure "Vt1" with the resistance R with respect to the reference voltage "5V" of the control unit 300. It is possible.

The thermostat 631 is arranged near the center of the heater 600, and when a predetermined temperature is reached, the internal contacts are separated and the thermostat 631 is held in an open state. Further, the thermostat 631 is connected between the heater control circuit 200 and the heater 600.

The heater control circuit 200 is a circuit that is connected to the commercial power supply 400 and supplies power to the DC power supply 410 and the heater 600 in the fixing device 30, and the amount of power supplied to the heater 600 is adjusted by the conduction ratio of the triacs 201a to 201f. doing. Such a heater control circuit 200 includes a relay circuit 210, a zero-cross detection circuit 220, a plurality of (here, 6) triacs 201a to 201f, and a plurality of (here, 6) triac drive circuits 231a to 231f. Have.

The relay circuit 210 is a circuit for cutting off the power supply to the fixing device 30 when the voltage output from the commercial power supply 400 is an abnormal value, and is connected to the commercial power supply 400. The relay circuit 210 is turned on and off according to the relay ON signal (RL-ON) transmitted from the CPU 301 of the control unit 300.

The zero-cross detection circuit 220 is a circuit that detects the zero-cross timing of the AC voltage output from the commercial power supply 400 and outputs the zero-cross signal ZX. The output zero-cross signal ZX is input to the control unit 300 and used to change the conduction ratio of the thyracs 201a to 201f, which will be described later.

In this embodiment, a plurality of triacs 201a to 201f are used in order to perform on / off control of power supply to the heater 600 and adjustment control of the power supply amount. The heater 600 has three heating elements 623a to 623c on the front surface (first surface) of the substrate 610 on the side where the heater 600 abuts on the inner peripheral surface of the fixing belt 650, and on the back surface (first surface) opposite to the front surface. Three heating elements 623d to 623f are also provided on the second surface). In FIG. 3, heating elements 623a to 623c on the front surface (lower side of the broken line in the figure) and heating elements 623d to 623f on the back surface (upper side of the broken line in the figure) are schematically shown side by side. Details of the heater 600 will be described later.

In this embodiment, six triacs 201a to 201f are provided in order to operate these six heating elements 623a to 623f individually. First, regarding the heating elements 623a to 623c provided on the surface of the substrate 610, the thyac 201a is connected to the heating element 623a, the thyac 201b is connected to the heating element 623b, and the thyac 201c is connected to the heating element 623c. Regarding the heating elements 623d to 623f provided on the back surface of the substrate 610, the thyrac 201d is connected to the heating element 623d, the thyac 201e is connected to the heating element 623e, and the thyac 201f is connected to the heating element 623f. In these triacs 201a to 201f, one end side connected to the heating elements 623a to 623f and the other end side opposite in the width direction are connected to the commercial power supply 400 via the zero cross detection circuit 220 and the relay circuit 210.

These thyristors 201a to 201f are connected to thyristor drive circuits 231a to 231f. The thyrac drive circuits 231a to 231f can individually turn on and off the thyristors 201a to 201f according to a heater ON signal (H-ON) appropriately transmitted from the CPU 301 of the control unit 300. When the triacs 201a to 201f are turned on, power is supplied to the heating elements 623a to 623f connected to the turned on triacs 201a to 201f, and the heating elements 623a to 623f generate heat.

Further, the thyrac drive circuits 231a to 231f can change the conduction ratio of the thyracs 201a to 201f according to the timing change of the heater ON signal (H-ON) transmitted from the CPU 301 of the control unit 300. By changing the conduction ratio of the triacs 201a to 201f, the amount of power supplied to the heating elements 623a to 623f changes. For example, if the conduction ratio of the triacs 201a to 201f is increased, the amount of power supplied to the heating elements 623a to 623f is increased, and the heating temperature of the heating elements 623a to 623f can be increased. On the other hand, if the conduction ratio of the triacs 201a to 201f is lowered, the amount of power supplied to the heating elements 623a to 623f is reduced, and the heating temperature of the heating elements 623a to 623f can be lowered.

The CPU 301 monitors the central temperature of the heater 600 as the voltage Vt1 described above, and controls the conduction ratios of the triacs 201a to 201f so that the heater 600 reaches the target temperature (around 200 ° C.). Specifically, the CPU 301 , The timing of the heater ON signal H-ON to the triac drive circuits 231a to 231f is changed.

In the control configuration of FIG. 3, a heating element for supplying electric power according to the size of the selected recording material is selected from the heating elements 623a to 623f. For example, when A4 size paper is selected as the recording material, the CPU 301 changes the conduction ratio of the thyrac 201b with an H-ON signal to adjust the power supply amount to the heating element 623b and control it to the target temperature. doing.

When A5 lateral feed (A5R) is selected, the CPU 301 changes the conduction ratio of the triac 201c with an H-ON signal to adjust the amount of power supplied to the heating element 623c and control it to the target temperature. ing. For other paper sizes, a heating element corresponding to the paper size is selected in the same manner as described above, and the temperature is controlled by controlling the amount of power supplied to the heating element.

When the CPU 301 detects that the central temperature of the heater 600 has risen by a predetermined value or more, the CPU 301 cuts off the power supply to the heater 600 by turning off the relay ON signal RL-ON and each thyrack ON signal H-ON. ..
[Details of heater]

Next, the details of the heater 600 of the present embodiment will be described with reference to FIGS. 4 (a) to 4 (c) with reference to FIG. FIG. 4A shows the back surface side of the heater 600, FIG. 4B shows the front surface side of the heater 600, and FIG. 4C shows a sectional view taken along the line AA of the heater 600. In FIGS. 4A to 4C, the arrow X in the figure indicates the rotation direction of the fixing belt 650 at the fixing nip portion N, that is, the conveying direction of the recording material (see FIG. 2).

The heater 600 as a heating member has a plurality of heating elements 623a to 623f provided on both sides of the substrate 610 and the substrate 610 and generates heat by energization, and is brought into contact with the inner peripheral surface of the fixing belt 650 to form a fixing belt. Heat 650. The substrate 610 is formed by using a material having insulating properties and heat resistance and further having high thermal conductivity, for example, a ceramic such as alumina or aluminum nitride.

The plurality of heating elements 623a to 623f have different lengths in the width direction intersecting the rotation direction of the fixing belt 650 in order to correspond to recording materials of a plurality of sizes. Each of these heating elements 623a to 623f is provided substantially parallel to the width direction. Further, on each surface, they are arranged at intervals in the transport direction of the recording material. Further, at least three heating elements are provided on the surface (first surface) of the substrate 610 on the side where the heater 600 comes into contact with the inner peripheral surface of the fixing belt 650. In this embodiment, three heating elements 623a to 623c are provided on the surface of the substrate 610. On the other hand, at least one heating element is provided on the back surface (second surface) opposite to the front surface of the substrate 610. In the present embodiment, the back surface of the substrate 610 is provided with three heating elements 623d to 623f, which are the same number as the front surface.

As shown in FIG. 4A, three heating elements 623d to 623f having different lengths in the width direction are printed and fired on the back surface of the substrate 610 using silver palladium (Ag / Pd) or the like. ing. The heating elements 623d to 623f are connected to three independent electrodes 622d to 622f on one end side in the width direction by a conductor pattern 624d to 624f formed of silver (Ag) or the like, and the other end side is connected to each other. It is connected to one common electrode 621B. Each of the three independent electrodes 622d to 622f is connected to the above-mentioned thyrac 201d to 201f (see FIG. 3). On the other hand, the common electrode 621B is connected to the commercial power supply 400 via the thermostat 631 described above, the zero cross detection circuit 220 of the heater control circuit 200, and the relay circuit 210 (see FIG. 3). As shown in FIG. 4C, the heating elements 623d to 623f and the conductor patterns 624d to 624f are covered with, for example, protective glass 611 having a thickness of 60 to 90 μm.

As shown in FIG. 4B, three heating elements 623a to 623c having different lengths in the width direction are formed on the front surface of the substrate 610 by using silver palladium (Ag / Pd) or the like on the front surface as well as the back surface. It is printed and fired. The heating elements 623a to 623c are connected to three independent electrodes 622a to 622c on one end side in the width direction by a conductor pattern 624a to 624c formed of silver (Ag) or the like, and the other end side is connected to each other. It is connected to one common electrode 621A. Each of the three independent electrodes 622a to 622c is connected to the above-mentioned thyrac 201a to 201c (see FIG. 3). On the other hand, the common electrode 621A is connected to the commercial power supply 400 via the thermostat 631 described above, the zero cross detection circuit 220 of the heater control circuit 200, and the relay circuit 210 (see FIG. 3). Similarly to the back surface, the heating elements 623a to 623c and the conductor patterns 624a to 624c on the front surface are also covered with protective glass 611 having a thickness of 60 to 90 μm, as shown in FIG. 4 (c).

In the case of the present embodiment, the

common electrodes

621A and 621B are formed at substantially the same positions on both sides of the substrate 610 in the width direction. On the other hand, the independent electrodes 622a to 622c and the independent electrodes 622d to 622f are formed at different positions in the width directions of both sides. However, the positional relationship between the

common electrodes

621A and 621B and the positional relationship between the independent electrodes 622a to 622c and the independent electrodes 622d to 622f are not limited to this.
[About the arrangement of each heating element]

Next, the arrangement of the plurality of heating elements 623a to 623f will be described with reference to FIGS. 4 (a) to 4 (c). In the heater 600 of the present embodiment, the heating element 623b having the longest length in the width direction among the plurality of heating elements 623a to 623f is provided on the surface of the substrate 610. Further, the three heating elements 623a to 623c provided on the surface are, in order from the one having the longest length in the width direction, the heating element 623b (first heating element), the heating element 623a (second heating element), and the heating element. It becomes a body 623c (third heating element). In this case, the heating element 623b having the longest length in the width direction with respect to the rotation direction of the fixing belt 650 is arranged between the heating element 623a and the heating element 623c. Further, the heating elements 623a to 623c have the heating element 623c and the heating element 623b in the direction from upstream to downstream in the rotation direction of the fixing belt (upstream to downstream in the direction in which the recording material is conveyed by the fixing nip portion N, arrow X direction). The heating elements 623a are arranged in this order.

On the other hand, at least three heating elements 623d to 623f are provided on the back surface of the substrate 610. In this embodiment, three heating elements are also provided on the back surface. That is, the number of heating elements provided on the front surface is the same as the number of heating elements provided on the back surface. Further, the three heating elements 623d to 623f provided on the back surface are, in order from the one having the longest length in the width direction, the heating element 623e (fourth heating element), the heating element 623f (fifth heating element), and the heating element. It becomes a body 623d (sixth heating element). In this case, the heating element 623e having the longest length in the width direction with respect to the rotation direction of the fixing belt 650 is arranged between the heating element 623f and the heating element 623d. Further, the heating elements 623d to 623f have the heating element 623d and the heating element 623e in the direction from upstream to downstream in the rotation direction of the fixing belt (upstream to downstream in the direction in which the recording material is conveyed by the fixing nip portion N, arrow X direction). The heating elements 623f are arranged in this order.

That is, in the present embodiment, the heating element having the longest length in the width direction is located at the center of each surface on both the front surface and the back surface, and the heating elements on the upstream side and the downstream side of the heating element are compared. In this case, the length of the heating element on the downstream side is longer in the width direction. The length of the fixing belt 650 of the heating element on each surface in the rotation direction is the same. In the present embodiment, the lengths of the fixing belts 650 of all the heating elements 623a to 623f in the rotation direction are the same.

Next, specific examples of each heating element 623a to 623f will be described. The six heating elements 623a to 623f arranged on both sides of the substrate 610 have different lengths, resistance values, and electric powers according to the lengths in the width direction of the plurality of sheets. Table 1 shows examples of heating elements 623a to 623f in the case of a commercial power supply of 100 V. The "heat generating body length" in Table 1 is the length in the width direction of the heating body.

Here, in the heater 600, the heat generated by the heating element on the back surface side of the substrate 610 is transferred to the fixing belt 650 via the substrate 610. Therefore, as compared with the heating element arranged on the front surface, the heating element arranged on the back surface side has a lower heat transfer efficiency to the fixing belt 650. In order to suppress a decrease in heat transfer efficiency to the fixing belt 650, it is desirable to arrange the heating element on the surface of the substrate 610. However, in a configuration having a plurality of heating elements having different lengths, if all of the heating elements are arranged on the surface of the substrate 610, the length of the heater 600 in the recording material transport direction becomes longer due to the arrangement of many heating elements. It will be long. Then, the pressing force for forming the fixing nip portion N must be increased. An increase in the pressing force causes an increase in the torque for rotationally driving the pressurizing roller 70, which is not preferable. Therefore, by arranging the heating elements on both sides of the substrate 610, a heater having a short length in the transport direction of the recording material and having many heating elements to accommodate various sizes can be obtained.

In the case of the present embodiment, if the length in the width direction (paper width) of the recording material S is long, the length in the width direction (heating element length) of the heating elements 623a to 623f is also formed long. In the case of the example shown in Table 1, the width direction lengths of the heating elements 623a to 623f are formed to be about 21 mm longer than the width direction lengths of the corresponding recording materials S, respectively. This is because the recording material S may be slightly displaced in the width direction and plunged into the fixing nip portion N when being conveyed to the fixing nip portion N (see FIG. 2), and even in such a case, the recording material S is appropriate. This is to secure a heating region of the fixing belt 650 so that it can be heated to the above.

Further, as can be understood from Table 1, the maximum electric energy of the heating elements 623a to 623f increases as the length in the width direction increases. Since the heating temperature of the heating elements 623a to 623f changes depending on the amount of electric power supplied, the larger the maximum amount of electric power, the higher the temperature at which the heating elements can generate heat. Therefore, if the electric power supplied to the heating elements 623a to 623f is the same, the longer the length in the width direction, the higher the temperature of the heating elements.

In the heater 600 of the present embodiment, the heating element 623b having the largest maximum electric energy and the heating element 623e having the second largest amount of electric power are provided on different surfaces of the substrate 610, respectively. The heating element 623b having the largest maximum electric energy, that is, the heating element 623b having the longest length in the width direction is provided on the surface of the substrate 610. As will be described later, among the three heating elements 623a to 623c provided on the surface of the substrate 610, the heating element 623b having the largest maximum electric energy is provided at the center of the fixing belt 650 in the rotation direction. On the other hand, the heating element 623e having the second largest maximum electric energy, that is, the heating element 623e having the second longest length in the width direction is provided on the back surface of the substrate 610. Among the three heating elements 623d to 623f arranged on the back surface of the substrate 610, the heating element 623e having the second largest amount of electric power is provided at the center of the fixing belt 650 in the rotation direction (X direction in the drawing). ing. In this way, the heating element with the largest maximum electric energy (longest length) among the three or more heating elements provided on one surface of the substrate is sandwiched between other heating elements. By setting the position, it is possible to reduce the distortion due to the heat of the substrate when the heating element having the largest maximum electric energy is heated.

By doing so, for example, even if the triac 701b fails and the heating element 623b having the largest maximum electric power constantly generates heat, the temperature difference between the front and back of the substrate 610 can be maximized to "2258W (1205 + 1053)". Can be suppressed. In the case of the present embodiment, it has been confirmed by experiments by the inventors that the substrate 610 is not deformed if the temperature difference between the front and back surfaces of the substrate 610 is suppressed to "3000 W" or less.

In the present embodiment, both the total value of the maximum electric energy of the heating elements 623a to 623c arranged on the front surface of the substrate 610 and the total value of the maximum electric energy of the heating elements 623d to 623f arranged on the back surface of the substrate 610 are both. , The substrate 610 is suppressed to "3000 W" or less, which is not deformed. Further, the difference between the total value of the maximum power amounts of the heating elements 623a to 623c arranged on the front surface of the substrate 610 and the total value of the maximum power amounts of the heating elements 623d to 623f arranged on the back surface of the substrate 610 is , It is preferable that it is as small as possible. In this embodiment, the front surface and the back surface are combined so that the difference between the maximum electric energy of the heating element arranged on the front surface of the substrate 610 and the maximum electric energy of the heating element arranged on the back surface of the substrate 610 is minimized. Heating elements were placed in each.

Further, in the heater 600 of the present embodiment, the heating element 623b having the largest maximum electric energy and the heating element 623c having the smallest maximum power among the plurality of heating elements 623a to 623f are combined and arranged on the surface of the substrate 610. Is preferable. In other words, of the plurality of heating elements 623a to 623f, the heating element 623b having the longest length in the width direction and the heating element 623c having the shortest length are arranged on the same surface of the substrate 610. The shortest heating element 623c is preferably arranged on the upstream side of the heating element 623b arranged in the center of the fixing belt 650 in the rotation direction (X direction in the drawing). In other words, on the upstream side and the downstream side, a heating element 623a having a length in the width direction longer than the heating element 623c is arranged on the downstream side.

On the other hand, it is preferable that the heating element 623e having the second largest electric energy and the heating element 623d having the second smallest power among the plurality of heating elements 623a to 623f are combined and arranged on the back surface of the substrate 610. In other words, of the plurality of heating elements 623a to 623f, the heating element 623e having the second longest length in the width direction and the heating element 623d having the second shortest length are arranged on the same surface of the substrate 610. The second shortest heating element 623d is preferably arranged on the upstream side of the heating element 623e arranged at the center of the fixing belt 650 in the rotation direction. In other words, on the upstream side and the downstream side, a heating element 623f having a length in the width direction longer than that of the heating element 623d is arranged on the downstream side.

With such a configuration, even if the heater control circuit 700 fails, the temperature difference between the front surface temperature and the back surface temperature of the substrate 610 can be suppressed to a temperature below the temperature at which the substrate 610 can be deformed. Heating elements 623a to 623f are separately provided on the front surface and the back surface. Specifically, as shown in Table 1 above, of the plurality of heating elements 623a to 623f, the heating element 623b having the longest width direction and the heating element 623e having the second longest length are different surfaces of the substrate 610. It is distributed to each. By distributing in this way, even if the heater control circuit 700 fails and a plurality of heating elements provided on one of the surfaces generate heat at the same time, the substrate 610 does not deform the temperature difference between the front and back surfaces of the substrate 610. It can be suppressed to the temperature difference or less (for example, 3000 W or less).

Next, the reason why it is preferable to arrange each heating element on each surface of the substrate 610 as described above will be described with reference to FIG. FIG. 5 shows the position of the heating element in the transport direction of the recording material of the fixing nip portion N when the A4 paper is continuously passed through the fixing nip portion N, and the temperature of the fixing belt 650 is maintained at a predetermined temperature. The result of investigating the relationship with the required power input to the heating element is shown. In FIG. 5, in order to show the difference in the input power depending on the location of the heating element, the power of each heating element is set to 1205 W, which is the same as that of the heating element 623b, and the heating elements are arranged upstream, in the center, and downstream in the transport direction of the recording material. It shows the case of.

The horizontal axis of FIG. 5 indicates the position of the heating element in the fixing nip portion N in the transport direction of the recording material, 0 mm corresponds to the center of the fixing nip portion N, the positive direction corresponds to the upstream, and the negative direction corresponds to the downstream. The recording material is transported from upstream to downstream. The vertical axis shows the power input to each heating element required to maintain the temperature of the fixing belt 650 at a predetermined temperature.

As shown in FIG. 5, the input power to the central heating element (0 mm position) is 680 W, the input power to the downstream heating element (position in the negative direction on the horizontal axis) is 790 W, and the power input to the upstream heating element (positive direction on the horizontal axis). The input power to (position) was 820 W. The smaller the input power, the higher the heating efficiency, so the heating efficiency is center> downstream> upstream. Therefore, it can be seen that the heating efficiency can be maximized by arranging the heating element in the center of the fixing nip portion N. It is considered that this is because the fixing nip portion N can be heated substantially evenly from the center to the upstream and downstream.

On the other hand, as shown in FIG. 2, the recording material S invades the fixing nip portion N from the lower side and passes upward (the recording material is conveyed from the right side to the left side in FIG. 2). Therefore, the time during which the recording material S is in contact with the fixing belt 650 is longer in the downstream than in the upstream. Therefore, the heating efficiency is higher when the heating element is arranged downstream than in the upstream. From the above, the highest heating efficiency can be obtained by arranging the heating element having a large electric power of the heating element, that is, having a long length in the width direction of the heating element at a position where the heating efficiency is high. This holds for both the front surface and the back surface of the substrate 610.

In the present embodiment, as described above, the length in the width direction of the heating element on both the front surface and the back surface of the substrate 610 is center>downstream> upstream with respect to the transport direction of the recording material, that is, the rotation direction of the fixing belt 650. Arranged to meet. Therefore, it is possible to provide a heater having excellent heating efficiency in a configuration having a plurality of heating elements on both sides of the substrate.
As described above, according to the present embodiment, by providing the longest heating element at a position sandwiched between other heating elements, it is possible to reduce the distortion of the substrate caused by energizing the longest heating element. .. Furthermore, it becomes possible to provide a heater having excellent heating efficiency.
<Second embodiment>

The second embodiment will be described with reference to FIG. In the first embodiment described above, a configuration in which three heating elements are provided on both sides of the substrate has been described. On the other hand, in the present embodiment, four heating elements are provided on both sides of the substrate 710. Since other configurations and operations are the same as those in the first embodiment described above, the same components will be omitted or simplified, and the parts different from the first embodiment will be mainly described below. ..

FIG. 6A shows the back surface of the substrate 710 of the heater 700 in this embodiment, and FIG. 6B shows the front surface. The arrow X in the figure indicates the rotation direction of the fixing belt 650 at the fixing nip portion N, that is, the conveying direction of the recording material (see FIG. 2).

The heater 700 as a heating member has a plurality of heating elements 723a to 723h provided on both sides of the substrate 710 and the substrate 710 and generates heat by energization, and abuts on the inner peripheral surface of the fixing belt 650 (FIG. 2). The fixing belt 650 is heated. The substrate 710 is formed by using a material having insulating properties and heat resistance and further having high thermal conductivity, for example, a ceramic such as alumina or aluminum nitride.

The plurality of heating elements 723a to 723h have different lengths in the width direction intersecting the rotation direction of the fixing belt 650 in order to correspond to recording materials of a plurality of sizes. Each of these heating elements 723a to 723h is provided substantially parallel to the width direction. Further, on each surface, they are arranged at intervals in the transport direction of the recording material. Further, at least three heating elements are provided on the surface (first surface) of the substrate 710 on the side where the heater 700 comes into contact with the inner peripheral surface of the fixing belt 650. In this embodiment, four heating elements 723a to 723d are provided on the surface of the substrate 710. On the other hand, at least one heating element is provided on the back surface (second surface) opposite to the front surface of the substrate 710. In the present embodiment, the back surface of the substrate 710 is provided with four heating elements 723e to 723h, which are the same number as the front surface.

As shown in FIG. 6A, four heating elements 723e to 723h having different lengths in the width direction are printed and fired on the back surface of the substrate 710 using silver palladium (Ag / Pd) or the like. ing. The heating elements 723e to 723h are connected to four independent electrodes 722e to 722h on one end side in the width direction by a conductor pattern 724e to 724h formed of silver (Ag) or the like, and the other end side is connected to each other. It is connected to one common electrode 721B. The heating elements 723e to 723h and the conductor patterns 724e to 724h are covered with, for example, protective glass 711 having a thickness of 60 to 90 μm.

As shown in FIG. 6B, four heating elements 723a to 723d having different lengths in the width direction are used on the front surface of the substrate 710 as well as on the back surface by using silver palladium (Ag / Pd) or the like. It is printed and fired. The heating elements 723a to 723d are connected to four independent electrodes 722a to 722d on one end side in the width direction by a conductor pattern 724a to 724d formed of silver (Ag) or the like, and the other end side is connected to each other. It is connected to one common electrode 721A. Similar to the back surface, the heating elements 723a to 723d and the conductor patterns 724a to 724d on the front surface are also covered with protective glass 711 having a thickness of 60 to 90 μm, for example.

Also in the case of this embodiment, the

common electrodes

721A and 721B are formed at substantially the same positions on both sides of the substrate 710 in the width direction. On the other hand, the independent electrodes 722a to 722d and the independent electrodes 722e to 722h are formed at different positions in the width directions of both sides. However, the positional relationship between the

common electrodes

721A and 721B and the positional relationship between the independent electrodes 722a to 722d and the independent electrodes 722e to 722h are not limited to this. Further, the control configuration of the heater 700 of the present embodiment has the same configuration as that of FIG. 3 of the first embodiment except that the number of the thyrac and the thyrac drive circuit differs depending on the number of heating elements.

Next, the arrangement of the plurality of heating elements 723a to 723h will be described. In the heater 700 of the present embodiment, the heating element 723b having the longest length in the width direction among the plurality of heating elements 723a to 723h is provided on the surface of the substrate 710. Further, three heating elements 723a to 723c out of the four heating elements 723a to 723d provided on the surface are the heating elements 723b (first heating element), in order from the one having the longest length in the width direction. It becomes a heating element 723c (second heating element) and a heating element 723a (third heating element). In this case, the heating element 723b having the longest length in the width direction with respect to the rotation direction of the fixing belt 650 is arranged between the heating element 723a and the heating element 723c. Of the four heating elements 723a to 723d provided on the surface, the length of the heating element 723d in the width direction is the shortest.

Further, for the heating elements 723a to 723d, the most upstream heating element 723d in the rotation direction of the fixing belt (direction in which the recording material is conveyed by the fixing nip portion N, arrow X direction) and the most downstream heating element 723a were compared. In this case, the heating element 723a is longer in the width direction than the heating element 723d. Further, of the heating elements 723a to 723d, the two

heating elements

723b and 723c having a long width direction are arranged between the heating element 723a and the heating element 723d having a shorter length in the width direction. ing. That is, the heating element having a long width direction is arranged on the center side of the fixing nip portion N (FIG. 2) in the arrow X direction. Further, as for the two

heating elements

723b and 723c, the heating element 723b having a longer length in the width direction is arranged downstream. That is, the heating element having the longest length in the width direction is provided on the downstream side of the center of the heater in the rotation direction, and is arranged between the plurality of heating elements. As described above, when the number of heating elements provided on one surface of the substrate is an even number, the longest heating element in the width direction is provided between the plurality of heating elements on the downstream side from the center in the rotation direction. On the other hand, when the number of heating elements provided on one surface of the base material is an odd number, the longest heating element in the width direction is provided in the center in the rotation direction.

On the other hand, three heating elements 723f to 723h out of the four heating elements 723e to 723h provided on the back surface are 723g (fourth heating element), in order from the one having the longest length in the width direction. It becomes a heating element 723f (fifth heating element) and a heating element 723h (sixth heating element). In this case, with respect to the rotation direction of the fixing belt 650, the heating element 723g having the longest length in the width direction is arranged between the heating element 723f and the heating element 723h. Of the four heating elements 723e to 723h provided on the back surface, the length of the heating element 723e in the width direction is the shortest.

Further, as for the heating elements 723e to 723h, the most upstream heating element 723e in the rotation direction of the fixing belt (direction in which the recording material is conveyed by the fixing nip portion N, arrow X direction) and the most downstream heating element 723h are compared. In this case, the heating element 723h is longer in the width direction than the heating element 723e. Further, of the heating elements 723e to 723h, the two

heating elements

723f and 723g having a long width direction are arranged between the heating element 723e and the heating element 723h having a shorter length in the width direction. ing. That is, the heating element having a long width direction is arranged on the center side of the fixing nip portion N (FIG. 2) in the arrow X direction. Further, as for the two

heating elements

723f and 723g, the heating element 723g having a longer length in the width direction is arranged downstream.

The length of the fixing belt 650 of the heating element on each surface in the rotation direction is the same. In the present embodiment, the lengths of the fixing belts 650 of all the heating elements 723a to 723h in the rotation direction are the same.

In the case of this embodiment, when a heating element having a long width direction is arranged on the center side of the fixing nip portion N, and further, when the most downstream and the most upstream heating elements are compared, the length in the width direction is long. A heating element with a long length is placed on the downstream side. Therefore, as described with reference to FIG. 5, it is possible to provide a heater having excellent heating efficiency in a configuration having a plurality of heating elements on both sides of the substrate.
<Other embodiments>

In each of the above-described embodiments, the configuration in which the same number of heating elements are provided on both sides of the substrate has been described, but the number of heating elements on both sides may be different. The present invention is applicable as long as it has at least three heating elements on the front surface and at least one heating element on the back surface.

According to the present invention, there is provided a fixing belt unit and a fixing device for an electrophotographic image forming apparatus or the like that can reduce the distortion of the substrate caused by energizing the longest heating element.

The present invention is not limited to the above embodiments, and various modifications and modifications can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are attached to make the scope of the present invention public.

This application claims priority on the basis of Japanese Patent Application Patent Application No. 2019-121149 submitted on June 28, 2019 and Japanese Patent Application Application No. 2019-12155 submitted on June 28, 2019. All of the contents are incorporated here.

Claims

A rotatable fixing belt for fixing the toner image on the recording material to the recording material,
It is provided with a substrate and a plurality of heating elements provided on both sides of the substrate and generating heat by energization, and a heating member that comes into contact with the inner peripheral surface of the fixing belt to heat the fixing belt.
The plurality of heating elements have different lengths in the width direction intersecting the rotation direction of the fixing belt.
At least three heating elements are provided on the first surface of the substrate on the side where the heating member comes into contact with the inner peripheral surface of the fixing belt, and the second surface of the substrate is opposite to the first surface. Multiple heating elements are provided on the surface,
Among the heating elements provided on the first surface in the rotation direction, the heating element having the longest length in the width direction is a fixing belt unit arranged between other heating elements.
When three heating elements are provided on the first surface and the first heating element, the front second heating element, and the third heating element are used in descending order of length in the width direction, in the rotation direction of the fixing belt, The fixing belt unit according to claim 1, wherein the third heating element is provided on the upstream side of the first heating element, and the second heating element is provided on the downstream side of the first heating element.
The heating element according to claim 1 or 2, wherein an odd number of heating elements are provided on the first surface, and the heating element having the longest length in the width direction is provided at the center of the heating member in the rotation direction. Fixing belt unit.
Three of the heating elements are provided on the second surface of the substrate.
In the heating elements provided on the second surface, when the fourth heating element, the fifth heating element, and the sixth heating element are used in order from the one having the longest length in the width direction, the first heating element is described in the rotation direction. The fixing belt unit according to claim 1, wherein the 6 heating element is provided on the upstream side of the 4th heating element, and the 5th heating element is provided on the downstream side of the 4th heating element.
The heating element according to claim 1, wherein an even number of heat generating values are provided on the first surface, and the heating element having the longest length in the width direction is provided on the downstream side of the center of the heating member in the rotation direction. Fixing belt unit.
The fixing belt unit according to any one of claims 1 to 5, wherein the number of the heating elements provided on the first surface is the same as the number of the heating elements provided on the second surface.
Among the plurality of heating elements provided on the first surface and the second surface, the heating element having the longest length in the width direction is any one of claims 1 to 6 provided on the first surface. The fixing belt unit according to item 1.
The total of the maximum power values of the heating elements provided on the first surface and the total maximum power values of the heating elements provided on the second surface are 3000 W or less, respectively, according to any one of claims 1 to 7. The described fixing belt unit.
Heating elements are provided on each surface so that the difference between the total maximum power value of the heating elements provided on the first surface and the total maximum power value of the heating elements provided on the second surface is minimized. The fixing belt unit according to any one of claims 1 to 8.